DEGRADATION AND STABILIZATION OF PVC IN BLENDS

Poly(vinylchloride) (PVC)was mixed with various poly(methacrylate)s, poly(carbonate)s and polymers containing nitrite groups (poly(acrylonitrile), poly(styrene-co-acrylonitrile), nitrile rubber, hydrogenated nitrile rubber) and/or C - C double bonds(nitrile rubber, high-impact poly(styrene)). The thermal stability was measured at 180-degrees-C in nitrogen, and the evolved HCl was detected by conductometry. It is shown that the nature of the ester group and the content of nitrile groups and C - C double bonds are the dominating factors for the thermal stability of poly(vinyl chloride) in these blends. An influence of the miscibility of PVC with the various blend components an the thermal stability can not be clearly detected. Differential scanning calorimetry (DSC) was used as a powerful method to study the stabilizer distribution of heterogeneous PVC/poly(styrene-co-acrylonitrile) and PVC/poly(methylacrylate) blends. It is shown that the stabilizer can be solubilized either in the PVC phase(PVC/poly(methylacrylate)) or in both phases of the blends PVC/poly(styrene-co-acrylonitrile)).